1. Field of the Invention
The invention relates to a disk drive, and more particularly, to an actuator having an absorption filter absorbing foreign materials in a disk drive and a disk drive having the same.
2. Description of the Related Art
Hard disk drives (HDDs), which are data storage devices used for computers, use read/write heads to reproduce or record data with respect to a disk. In the HDD, the read/write head performs its functions while being moved by an actuator to a desired position, wherein the read/write head is lifted to a predetermined height from a recording surface of a rotating disk.
FIG. 1 is a plan view illustrating the configuration of a conventional hard disk drive. FIG. 2 is a magnified perspective view illustrating a ramp and a suspension portion of the actuator shown in FIG. 1. Referring to FIGS. 1 and 2, a conventional hard disk drive includes a spindle motor 12 installed on a base plate 10. A disk 20, which is one or more disks, is installed on the spindle motor 12. An actuator 30 is installed to move a rear/write head (not shown) for reproducing and recording data to a predetermined position on the disk 20. The actuator 30 includes a swing arm 32 rotatably coupled to a pivot bearing 31 installed on the base plate 10, a suspension 33 installed at one end portion of the swing arm 32 and supporting a slider 34, on which the head is mounted, toward a surface of the disk 20 to be elastically biased, and a voice coil motor (VCM) to rotate the swing arm 32. The voice coil motor includes a VCM coil 36 coupled to the other end portion of the swing arm 32, a lower yoke 37 installed below the VCM coil 36, and a magnet 38 attached to an upper surface of the lower yoke 37. Although not shown in the drawing, the voice coil motor may further include an upper yoke installed above the VCM coil 36 and a magnet attached to a lower surface of the upper yoke.
The voice coil motor having the above configuration is controlled by a servo control system to rotate the swing arm 32 in a direction following the Fleming's left hand rule by the interaction between current applied to the VCM coil 36 and a magnetic field formed by the magnet 38. That is, when the power of the hard disk drive is on and the disk 20 starts to rotate in a direction D, the voice coil motor rotates the swing arm 32 counterclockwise, that is, in a direction A, to move the slider 34 on which the head is mounted toward a position above the recording surface of the disk 20. The slider 34 is lifted to a predetermined height, for example, about 13 nm, from the surface of the disk 20 by a lift force generated by the rotating disk 20. In this state, the rear/write head mounted on the slider 34 reproduces or records data with respect to the recording surface of the disk 20.
When the hard disk drive does not operate, (that is, the disk 20 stops rotating) the head is parked at a position out of the recording surface of the disk 20 so that the head does not collide against the recording surface of the disk 20. The head parking system may be employed using a contact start stop (CSS) method or a ramp loading method. In the CSS method, a parking zone where data is not recorded is provided at or near an inner circumferential side of the disk 20 and the head is parked in the parking zone in a contact or near contact manner. However, in a head parking system adopting the CSS method, since the parking zone needs to be provided at or near the inner circumferential side of the disk 20, data storage space is reduced. Thus, to meet the recent demands of a higher data recording density, a head parking system adopting the ramp loading method is widely used because it can secure a larger data storage space.
In the ramp loading method, a ramp 40 is installed at the outside of the disk 20 and the head is parked on the ramp 40. To this end, the suspension 33 has an end-tab 35 extended therefrom, which contacts a support surface 41 of the ramp 40. The end-tab 35 generally has a shape convex toward the support surface 41 to reduce a contact area between the end-tab 35 and the support surface 41 of the ramp 40.
When the power of the hard disk drive is off and the disk 20 stops rotating, the voice coil motor rotates the swing arm 32 clockwise, (that is, in a direction B). Accordingly, the end-tab 35 is unloaded from the disk 20 and moved to the support surface 41 of the ramp 40. In contrast, when the power of the hard disk drive is on and the disk 20 starts to rotate, the end-tab 35 is unloaded from the support surface 41 of the ramp 40 and moved above the disk 20 by the rotation of the swing arm 32.
In a state in which the head is parked on the ramp 40, when an external impact or a vibration is applied to the disk drive, the actuator 30 rotates and moves toward the recording surface of the disk 20 from the ramp 40. In this case, the head contacts the recording surface of the disk 20 so that the read/write head and the recording surface of the disk 20 may be damaged. Thus, when the disk 20 stops rotating and the head is parked on the ramp 40, the actuator 30 should be locked at a predetermined position so as to not rotate. For this purpose, an actuator latch 50 is provided.
Foreign materials, such as particles or gas, are generated in the hard disk drive having the above configuration. For example, when the end-tab 35 is moved toward the disk 20 or the support surface 41 of the ramp 40, a sliding friction is generated between the end-tab 35 and the support surface 41 of the ramp 40. After repeating such movements, the support surface 41 of the ramp 40 (often formed of plastic) is abraded so that particles are generated. FIG. 3 shows particles adhering on and around the end-tab 35. When the head lifted above the surface of the disk 20 collides against the surface of the disk 20 by an external impact or vibration, particles are generated due to the friction and abrasion between the head and the disk 20. Also, the hard disk drive has many parts that are electrodeposition-coated or nickel-coated and made of plastic, such as the ramp 40. In a burn-in process to prove servo compensation, defect free, and head performance, or when a particular time passes after the disk drive operates, the disk drive is in a high temperature state. In the high temperature state, gas is generated from the parts of the disk drive. Gas molecules perform Brownian motions in the disk drive and chemically react with one another or collide against one another, such that particles having a size of several hundred nanometers may be formed.
The particles flow in the hard disk drive following the airflow generated by the rotation of the disk 20. The size of the flowing particle varies from several nanometers to several hundred nanometers. A particle larger than an interval between the head and the disk 20, that is, a flying height of the head, collides with the head and changes the posture of the head. Accordingly, the head contacting the disk 20 scratches the recording surface of the disk 20 and damages a magnetic signal. Also, a read/write sensor of the head is damaged by the collision between the particle and the head, thereby causing the read/write sensor not to function properly. In addition, particles having a size smaller than the flying height of the head intrude between the head and the surface of the disk 20, thereby damaging the head or scratching the surface of the disk.
Ultra-light, high capacity, and compact hard disk drives have recently been developed. Accordingly, the storage capacity of a disk is greatly increased. For example, the track density and the track width of the disk is presently about 90,000 TPI (track per inch) and about 11μ inch, respectively. It is expected that the track density and the track width of the disk will be 130,000 TPI and 7.7μ inch, respectively, in the future. Consequently, the flying height of the head is gradually decreased so that the head is easily damaged by tiny particles and the magnetic signal on the disk surface is easily damaged by small scratches.
Thus, to solve the above problems, foreign materials such as particles or gas generated in the disk drive need to be collected and removed. Conventionally, as shown in FIG. 1, a circulation filter 60 is provided at a corner of the base plate 10 to filter foreign materials, such as particles, included in the airflow in the hard disk drive. However, the circulation filter 60 does not have a satisfactory filtering effect.
FIG. 4 shows the result of simulation of the distribution of flow speed of particles on and around the surface of a rotating disk in the conventional hard disk drive shown in FIG. 1. Referring to FIG. 4, an airflow is formed by the rotation of a disk in the disk drive. Particles in the disk drive are moved together with the airflow. The flow speed of the particles is proportional to the flow speed of the air. Accordingly, the flow speed of the particles is faster as the particles are located closer to the outer circumferential side of the disk while the flow speed of the particles is slower as the particles are located closer to the inner circumferential side of the disk. When the conventional circulation filter 60 is used, there is nearly no flow of the particles and the particles hardly exist in a region R where the conventional circulation filter 60 is disposed. Such low speed or non-flow of the particles at the region R indicates that the air is hardly input to the circulation filter 60. Therefore, the conventional circulation filter does not work properly in collecting the particles.
In order for the circulation filter 60 to exert its maximum function of collecting the particles, there needs to be provided a structure to guide the airflow toward the circulation filter or move the position of the circulation filter 60. To guide the airflow toward the circulation filter 60, the interval between the base plate 10 and the disk 20 needs to be increased such that the air reaches the circulation filter 60. However, such a change causes a change in the airflow speed in a circumferential direction and up/down directions of the disk 20, thereby altering a pressure applied to the surface of the disk 20, causing the disk 20 to vibrate. The vibration increases the track misregistration (TMR) so that performance of the hard disk drive is negatively affected. As a result, changing the structure of the base plate 10 to guide the airflow toward the circulation filter 60 is not a desirable solution.
FIG. 5 shows an actuator of a magnetic disk apparatus disclosed in Japanese Patent Application Publication No. 2001-76478. Referring to FIG. 5, a slider 72 on which a head is mounted and a gas absorption member 80 are attached to a swing arm 71 of an actuator 70. The gas absorption member 80 is attached to a surface of the swing arm 71 facing the disk 20 to absorb contaminants on a surface of the hard disk. However, the thickness of the gas absorption member 80 is limited since it is attached to the surface of the swing arm 71 facing the disk 20. That is, the thickness of the gas absorption member 80 cannot be greater than the interval between the swing arm 71 and the disk 20 and thicker than the thickness of the slider 72. Thus, since the gas absorption member 80 adhering to the surface of the swing arm 71 facing the disk has a very small thickness, it can collect gas having a size of several nanometers but cannot easily collect particles having a size of several hundred nanometers. Also, since the gas absorption member 80 is arranged parallel to a direction of airflow, an efficiency in collecting gas and particles is low.
The gas absorption member 80 can be applied to only the actuator 70 having a structure in which a plurality of swing arms having a shape of a thin plate are stacked. However, when a plurality of swing arms constitute a signal block having an “E” shape, since the interval between the swing arms is narrow, it is difficult to attach the gas absorption member on the surface of the swing arm facing the disk.